For the purpose of this topic, "drug of abuse" is defined as a drug, chemical, or plant product that is known to be misused for recreational purposes. Although drug of abuse (DOA) testing is routinely performed in the clinical setting, many studies evaluating such screening have failed to demonstrate clinical benefit, and most toxicologists suggest obtaining such testing only when there is a clear indication [1-3].

The apparent simplicity of the results provided with a DOA screen, typically reported as negative or positive for the presence of a given drug, can mislead clinicians into believing that DOA testing is straightforward and the results easy to interpret. In fact, DOA testing is extremely complex and proper interpretation requires specialized knowledge. Several studies of DOA testing show that many clinicians who regularly order DOA tests do not understand proper testing techniques, which drugs are detected, or how to properly interpret positive and negative results [4-6]. Proper interpretation of the results of a DOA screen depends upon the clinical context. Clinicians must consider the type of testing being performed, level of suspicion for drug use or exposure (ie, pretest probability), purpose of obtaining the test, and likelihood of false-positive and false-negative results.

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